A Combined Asphaltene Study Relating Kinetic Aggregation and Deposition Parameters to Thermodynamic Driving Forces

This study discusses experimental results of asphaltene aggregation and deposition using various n-alkanes as precipitants to destabilize asphaltenes. The amount of asphaltenes destabilized with different precipitants and at various concentrations was obtained, and the collision efficiency for asphaltene aggregation was calculated using a geometric population balance. The results revealed that for a fixed volume fraction of precipitant, the asphaltene-asphaltene collision efficiency decreased with higher carbon number precipitants. Furthermore, decreasing the precipitant concentration resulted in lower collision efficiencies, in agreement with previous studies. A correlation was developed to relate between the collision efficiency and a thermodynamic driving force of the differences in asphaltene and surrounding liquid solubility parameters with various precipitants and precipitant concentrations. In addition, the tendency for asphaltenes to deposit was measured using capillary flow experiments with varied precipitants and precipitant concentrations. The results revealed that the time for asphaltene deposits to be detected can be estimated using a similar solubility parameter correlation. The results also demonstrated that the deposition behavior of asphaltenes can be normalized by considering the concentration of precipitated asphaltenes flowing through the apparatus. Scanning electron microscopy (SEM) images of the asphaltene deposits were obtained and used to assess the mixing of oil and precipitant. This study unifies two independent asphaltene processes under a single thermodynamic framework.